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1036                          Appendix VI.

the addition of an attachment carrying a spindle similar to g,
while a pulley like e is placed on the existing spindle. By this
apparatus holes of a depth of 40 ins. have been trued, and pro-
vision is made for various diameters to a minimum of f in.

The Surface Grinding Machine in Fig.  936 is built on the

lines of a planing machine.    Thus, on a bed A, a table B travels

backward and forward,  to  which is fastened the work  to be

ground.   At each reciprocation of the table the tappets c or D

strike a lever E, which, acting by cranks and rods on the forks

F F, put in gear alternately a crossed or open strap connecting the

pulleys at G with the countershaft pulley^ from which the table is

driven by rack and pinion in the ordinary manner.    By the same

tappet action the shaft H is rotated through a spur-gear connec-

tion, and a connecting rod j moves a rack K, which in turn moves

a ratchet L by a pawl, causing the grinding head to- traverse across

the face of the work.    The wheel/ is for hand setting.    The

standards M M carry a slide N that supports the saddle P, and

a forked bracket Q has two bearings for the emery wheel R.

When the work is being set, a fine adjustment between the wheel

R and the table is provided by means of the screw or clamp s,

which turns the forked bracket round the pin e as a centre.    This

movement is also used for the advance of cutting depth, which is

done after each complete traverse of the wheel across the table ;

and as the centres u, <?, and T are practically in one line, the

length of driving belts from drum T to the pulleys u u on the

wheel spindle is unchanged by the movement of the wheel bracket.

The wheel R is set to the work in the first instance by unbolting

the cross slide N from the standards, and raising or lowering it by

the hand wheel v and screws w w.   The fast and loose pullies at

g take the main driving belt, and the pulley h drives the long

drum T for the emery wheel.    The water pump x is driven from

the countershaft, the return water flowing from the table through

pipe Y; and an adjustment for the wear of wheel bearings is

obtained by the screw z.   The grinding wheel is driven by two

open belts to the pullies u u in order to cause an even pressure

on the bearings^ and the wheel is reversed at every change ot

table motion by means of a reversing box, rack and wheel, not

shewn in the diagram.                              t